# Structural origin of long-range proximity effect in highly disordered fractal MgO/MgB2 nanocomposites: Roles of interface, geometry, and defect

https://mdr.nims.go.jp/datasets/83f31b27-b3cd-41e7-b9db-f0773237c04f

## File

- [1972813_1_art_file_25655210_t3l2d0.pdf](https://mdr.nims.go.jp/filesets/c2969c77-e44c-4c59-9dac-2de35f312854/download) ([Detail](https://mdr.nims.go.jp/filesets/c2969c77-e44c-4c59-9dac-2de35f312854.md))

## Id

83f31b27-b3cd-41e7-b9db-f0773237c04f

## Local identifier



## Visibility

open_to_public

## State

published

## Created at

2025-12-19T02:26:36.466864Z

## Updated at

2025-12-19T03:01:04.396482Z

## Published at

2025-12-19T11:30:49.186004Z

## Doi

https://doi.org/10.48505/nims.6042

## First published url

https://doi.org/10.1063/5.0293448

## Date published

2025-10-28

## Recorded date published

2025-10-28

## Resource type

journal_article

## Manuscript type

accepted_manuscript

## Collection



## Title

- title: 'Structural origin of long-range proximity effect in highly disordered fractal
    MgO/MgB2 nanocomposites: Roles of interface, geometry, and defect'
  title_type: original
  lang: en

## Description

- description: The emergence of global phase coherence due to proximity effect in
    heterogeneous and disordered superconductor systems has been an issue of long-standing
    interest. Recently, we have reported that a highly disordered fractal MgO/MgB2
    nanocomposite exhibits bulk-like superconducting properties with isotropic pinning,
    showing an excellent phase-coherent capability irrespective of the low volume
    fraction (~30 vol. %) of MgB2 [Uchino et al., Phys. Rev. B 101, 035146 (2020);
    Teramachi et al,, Phys. Rev. B 108, 155146 (2023)]. In this work, we show from
    3D focused ion beam scanning electron microscopy data that in the nanocomposite,
    a complex MgO/MgB2 microstructure spreads isotropically throughout the sample
    with a constant fractal dimension of ~1.67. Atomic-resolution scanning transmission
    electron microscopy has revealed that the interfaces are atomically clean and
    free from amorphous grain boundaries. Detailed ac susceptibility measurements
    have demonstrated a smooth crossover from an intragranular to an intergranular
    superconducting regime. Also, spatially-resolved cathodoluminescence measurements
    have demonstrated that oxygen vacancies in the MgO-rich phase tend to aggregate
    near the MgO/MgB2 boundary regions, forming long channels of oxygen vacancies
    through the nanocomposite. These channels of oxygen vacancies are likely to be
    responsible for the long-range carrier transfer and the related proximity effect
    via coherent tunneling of charge carriers among the oxygen vacancy sites. Our
    results imply that the fractal-like MgO/MgB2 microstructure with atomically clean
    interfaces will induce the phase coherent transport of charge carries in the MgO-rich
    regions, leading to the observed long-range proximity effect and the resulting
    bulk-like superconductivity in this highly disordered system.
  description_type: abstract
  lang: und

## Creator

- name: Iku Nakaaki
  role: author
- name: Aoi Hashimoto
  role: author
- name: Shun Kondo
  role: author
- name: Yuichi Ikuhara
  role: author
- name: Shuuichi Ooi
  role: author
  orcid: https://orcid.org/0000-0003-2129-0310
  organization: National Institute for Materials Science
- name: Minoru Tachiki
  role: author
  orcid: https://orcid.org/0000-0002-6033-3515
  organization: National Institute for Materials Science
- name: Shunichi Arisawa
  role: author
  orcid: https://orcid.org/0000-0001-8155-9401
  organization: National Institute for Materials Science
- name: Akiko Nakamura
  role: author
  organization: National Institute for Materials Science
- name: Taku Moronaga
  role: author
  orcid: https://orcid.org/0000-0002-6915-0627
  organization: National Institute for Materials Science
- name: Jun Chen
  role: author
  orcid: https://orcid.org/0000-0003-4272-2653
  organization: National Institute for Materials Science
- name: Hiroyo Segawa
  role: author
  orcid: https://orcid.org/0000-0002-7198-8410
  organization: National Institute for Materials Science
- name: Takahiro Sakurai
  role: author
- name: Hitoshi Ohta
  role: author
- name: Takashi Uchino
  role: author

## Contact agent



## Publisher

organization: AIP Publishing

## Managing organization



## Keyword

- subject: nanocomposite
  schema: not_defined
- subject: MgO/MgB2
  schema: not_defined
- subject: Defects
  schema: not_defined

## Rights

- description: Copyright 2025 Author(s). This article is distributed under a Creative
    Commons Attribution (CC BY) License.
  identifier: https://creativecommons.org/licenses/by/4.0/
  date_licensed: 2025-10-22

## Other identifier(s)



## Data origin

- data_origin_type: other

## Embargo



## Journal

- title: Journal of Applied Physics
  issn: '00218979'
  volume: '138'
  issue: '16'
  article_number: '163902'

## Conference



## Related item



## Funding

- identifier: JPMXP1223NM0163, JPMXP1223MS1024 and JPMXP1224MS1017
  funder_name: Ministry of Education, Culture, Sports, Science and Technology
  description: ARIM

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## Fileset

- id: c2969c77-e44c-4c59-9dac-2de35f312854
  filename: 1972813_1_art_file_25655210_t3l2d0.pdf
  content_type: application/pdf
  size: 1774188
  md5: f7d6172fe5c1ba71f4010c25f977058b

## Thumbnail

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filename: 1972813_1_art_file_25655210_t3l2d0.pdf